1. Field of the Invention
The present invention relates to a method and a system for distribution of fluidizable materials. In particular the invention relates to distribution of fluidizable materials such as fluoride and/or aluminium oxide (alumina) within an electrolysis facility for the production of aluminium.
2. Description of Related Art
NO patent 175876 describes an apparatus for transport of powder materials by fluidizing the materials. The apparatus comprises an enclosed first fluidized channel for distribution of materials from a reservoir to a plurality of outlets. At each outlet there are arranged feeding devices for individual feeding of materials, such as alumina, to separate feeding holes in the crust of an electrolysis cell. The channel for distribution of materials comprises two horizontally divided sections where the sections are divided by means of a porous wall. The upper section is completely filled with fluidized materials, while the lower section act as a distribution chamber for fluidizing gas. The lower section is provided with fluidizing gas by means of a fan. The mentioned feeding devices comprise at least one second fluidized channel having plural outlets shaped as downwardly directed tubes. The outlets are surrounded by a casing having feeding holes in its bottom. The downwardly directed tubes end above the bottom part of the casing, and material leaving the outlets will be blocked as the level of material in the casing reaches a certain level. As materials are consumed, the level in the casing will drop and the outlets will be free of materials. Followingly, materials will start to flow into the casing from the reservoir through the first fluidizing channel and into the feeding device via the second fluidizing channel. To obtain this self-controlled feeding, the channels have to be fluidized continuously by the fan. Further, in the system the materials will be transported in accordance with one hydraulic step, and as a consequence of this, the vertical level between the uppermost material storage and the lowermost material outlet becomes high. In an electrolysis facility, such fluidized channels may have an extension of several hundred meters while the angular decline of the channel may be some degrees. Under certain unwanted circumstances such high static pressure differences in the transport system may lead to an uncontrolled transportation of materials such as rapid drainage of materials from the storage with a resulting undesired over-feeding of materials to the electrolysis cell as a consequence. Further, the energy consumed in the described system will be relatively high because the system is likely to be driven in a continuously fluidizing modus to operate in a satisfying manner.